1. Field of the Invention
The present invention relates to a light source apparatus having a solid light source element and a phosphor.
2. Description of the Related Art
Conventionally, there has been known a light source apparatus in which a light source element such as a LED chip or the like is covered by a translucent resin mold member having a phosphor (for example, refer to Japanese Patent Laid-open No. 2001-77433). The conventional light source apparatus emits to the outside of the translucent rein mold member a light beam of a combination color combined from a light beam emitted from the solid light source element and a fluorescence beam generated according to the excitation of the phosphor by the light beam emitted from the solid light source element.
The light source apparatus mentioned above has been applied as a light source in lighting equipments, headlamps of a vehicle and the like in rapid progress, thus, it has been required that the light source apparatus emit a light beam of a high intensity in a high efficiency. In response to the requirement, there have been disclosed in, for example, Japanese Patent No. 4140606 and Japanese Patent Laid-open No. 2007-157766, arts for improving light-emitting intensity and light-emitting efficiency of a GaN light-emitting semiconductor element used as the solid light source element.
In the light source apparatus disclosed in Japanese Patent Laid-open No. 2001-77433, in order to make the light source apparatus emit the combination light combined from the light beam emitted from the solid light source element and the fluorescence beam from the phosphor in a high efficiency and a high output, it is necessary to improve not only the light-emitting intensity and light-emitting efficiency of the solid light source element but also the light-emitting intensity and light-emitting efficiency of the fluorescence beam from the phosphor.
However, generally the light-emitting intensity of the fluorescence beam from the phosphor has a saturation characteristic relative to the light-emitting intensity of the solid light source element (incident intensity of an excitation light beam to the phosphor). Therefore, when the light-emitting intensity of the solid light source element reaches to a certain extent, even though the light-emitting intensity of the solid light source element increases, the light-emitting intensity of the fluorescence beam from the phosphor will not increase particularly.
The reasons why the light-emitting intensity of the phosphor will become saturated may be given as the follows: an exciton excited from the phosphor releases heat (become a phonon) when returning to the ground state via a non-radiation process, the released heat warms up the phosphor to have a temperature rise which deteriorates the light-emitting efficiency of the phosphor; or the excitation density (the amount of excitons generated from a unit volume of the phosphor) becomes high to give birth to an excitation saturation (saturation of the excitation density) which deteriorates the light-emitting efficiency of the phosphor
Therefore, in order to improve the light source apparatus to a high efficiency and a high output, it is desired to inhibit the above-mentioned reasons as much as possible.